The present invention relates to a frequency converting receiver; and, more particularly, to a monolithic microwave integrated circuit(MMIC) frequency converting receiver which employs field effect transistors(FETs) and is used in wireless/mobile communication systems.
Recently, to accommodate the tremendously increasing wireless communications demand, the need of a large capacity communication method is increasing. As a result, there has been proposed a digital scheme capable of accommodating a lot of users compared to a conventional analog scheme and there are being developed mobile communications systems providing services in various frequency bands. As examples, there are a cellular at about 900 MHz and a personal communications services(PCS) at about 1.9 GHz which is presently providing communications services, and international mobile telecommunications 2000 (IMT2000) at about 2.1 GHz and a wireless local loop(WLL) at about 2.4 GHz which will be served sooner or later.
Further, portable terminals used in the above various communications services have been developed depending on the communications systems. And the down converter IC chips used in the potable terminals of various communications services have own specific purpose and operating frequency.
At this time, there is increasing the demand of a multi-band, multi-mode portable terminal capable of serving all kinds of communications services by using one portable terminal and, thereafter, it is necessary to develop a wideband microwave frequency converting receiver so as to develop the multi-band, multi-mode portable terminal.
In general, the microwave frequency converting receiver comprises a low-noise amplifier(LNA) for detecting and amplifying weak radio frequency signals(referred to as xe2x80x9cRF signalsxe2x80x9d hereinafter), a frequency mixer for modulating or mixing small RF signals and large local oscillator signals(referred to as xe2x80x9cLO signalsxe2x80x9d hereinafter) to thereby produce signals having sum, difference(intermediate frequency signal referred to as xe2x80x9cIF signalxe2x80x9d hereinafter) or multiple frequencies of the RF signals and the LO signals and a balun and IF signal amplifier for producing complementary signals based on a single signal.
The conventional frequency converting receiver shown above is produced according to a hybrid scheme manufacturing a whole receiver by assembling its components. Therefore, although the frequency converting receiver is made as an MMIC, it is only applicable to one system whose operating frequency is within a narrow frequency band and corresponds to that of the receiver. This type of conventional frequency converting receiver for the hand held phone application is disclosed in an article published by A. Brunel et al., entitled xe2x80x9cA DOWNCONVERTER FOR USE IN A DUAL-MODE AMPS/CDMA CHIP SETxe2x80x9d, Microwave journal, pp20xcx9c42, February 1996. A down converter IC, which operates in frequency range of 500xcx9c1900 MHz, is disclosed in an article by L.Reynolds, xe2x80x9cDownconverter IC processes Signals From 500 To 1900 MHz, Microwaves and RF, pp134xcx9c140, July, 1997xe2x80x9d, where this chip set is employed in PCS application. Another type of the conventional frequency converting receiver is demonstrated in an article by Mark William et al., entitled xe2x80x9cGaAs RF ICs TARGET 2.4 GHz FREQUENCY BANDxe2x80x9d, Microwaves and RF, pp111xcx9c118, July, 1994, which may have potential of application in WLL system. Another type of down converters for satellite communication is disclosed in U.S. Pat. Nos. 5,528,769 and 5,649,312 issued on Jun. 18, 1996 and Jul. 15, 1997. Like above down converter ICs, most developed down converter had the specific operating frequency depending on the communication system. And there is no a down converter MMIC which can be applied to a multi band, multi mode portable terminal. Thereafter, it is difficult to apply the receiver to a receiving end of an RF unit of all of communications systems.
Consequently, there is required to develop a wideband microwave frequency converting receiver applicable to the RF unit which can be used in all of the wireless/mobile communications systems and the wideband microwave frequency converting receiver should have low-noise, high conversion gain and high linearity characteristics over a wide frequency band.
In addition, the portable terminal is continuously developed to have smaller size and lighter weight. Since a capacitor having a low capacity in order to reduce the weight of the portable terminal, it is necessary for the portable terminal to use components operating with low power consumption so as to extend its operating time. And, in order to manufacture the portable terminal having smaller size and lighter weight, it is also necessary to reduce the sizes of the components constituting the portable terminal. Further, as the number of subscribers of the mobile telephone system increases, a portable terminal having an advanced transmitting and receiving characteristic(specially, low-noise and high linearity characteristics) is required. Therefore, the performances of the components constituting the portable terminals should be also improved. In particular, microwave components which are core components of the portable terminal are being developed to the smallization through the use of an MMIC scheme, low-cost by a chip smallization scheme and low power by the improvement of a circuit structure.
Herein, the MMIC is referred to as a circuit employing active and passive devices integrated in a single semiconductor wafer. Compared with a conventional circuit employing individual devices therein, it is possible to reduce the size and weight of a circuit integrated in the MMIC since the pitches of devices constituting the circuit can be reduced. Further, since parasitic components due to the packaging of individual devices are originally eliminated, the availability of a frequency bandwidth can be substantially improved. Therefore, the trend is that the RF components of the wireless/mobile communications system are integrated into the MMIC in order to mass-produce a low cost, small size and light weight wireless/mobile communications equipment(e.g., mobile communications terminal) with low cost and good reproduction characteristics. The most important subject is to reduce the size of the MMIC since the manufacturing cost of the MMIC increases proportional to its size.
Therefore, it is required to develop a wideband frequency converting receiver which can be used in all of the wireless/mobile communication systems such as the cellular, PCS, WLL and IMT2000 and, further, integrated into the MMIC which results in mass-producing a low cost microwave frequency converting receiver applicable to the RF unit with low cost and good reproduction characteristics, which has low power consumption, low-noise, high gain and small size characteristics.
It is, therefore, a primary object of the present invention to provide a microwave frequency converting receiver applicable to an RF unit, which can be used in all of wireless/mobile communications systems such as cellular, PCS, WLL and IMT2000 systems and, further, has low power consumption, low-noise, high gain and small size characteristics.
In accordance with the present invention, there is provided a multi-band and multi-mode frequency converting receiver for use in a wireless mobile communications system, comprising: a wideband low-noise amplifier for amplifying a radio frequency input signal; a frequency mixer for producing an intermediate frequency signal having a relatively high linearity by mixing a local oscillator frequency signal and the amplified radio frequency signal outputted from the wideband low-noise amplifier; an intermediate frequency amplifier for producing a final intermediate frequency signal by amplifying the intermediate frequency signal derived from the frequency mixer; and an input matching circuit for receiving a microwave signal within a frequency band of the wireless mobile communications system, impedance-matching the received microwave signal to the radio frequency input signal of the wideband low-noise amplifier and determining an operating frequency band of the frequency converting receiver.